Electronic frequency-control device



-ll LANGE v ELECTRONIC FRE I Eu'YwoMRoL DEVICE Filed Oct. 30, 1943' s smu -shut; 1

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-. m INVENT'ORQ Aug. 20,1946. s. H1 muss 7 .ELECTRONIQ FREQUENCY-CONTROL DEVICE I Filed Oct. .30, 1943- s sheets-shea 2 .x ne

Ma wuiiktv U m u o Patented Aug. 20, 1946 "ELECTRGNIC"FREQUENCY-CONTROL Edward H. Lange, Baltimorey M d. "Application October '30, 1943, Serial No. 508*;367

. l'i Claims.

-t napertains to =electr-onic control devices for yltag'afrequency intercontrol, and more particularly to devices for seGlllil-lgw high "degree of frequency-stabilityandwave-form con- -tro1,L forproduction-of either 4 substantially pure 7 sine-waves or -waves -rich in harmonics such -.as rectangular or saw tcoth waves, with La .hi'ghflegree f frequency-stability, lover .a rangeaofi low or audio -and -super-audio frequencies, or; oveiua range of high orMradio-frequencies, with 2 frequency-stability substantially independent. .of variations of thermionic-tube resistancetand; network 1 resistance over ;the high frequency range, and independent of thermionic: tube resistance over the low frequency-range ;..for. providing. sim- -ple thermionic :means determining a .resultant output-voltage asto maXim-um voltageandzwaveform from. sinusoidal input-voltages, and roen- 4 trolling .the characteristics of the output-3101a ageswith .facility lover. a Wide. range of: modificationsiofL these. characteristics,including. the limiting of the output voltages to .aconstant:value, independent of. increases .in value of the. inputvoltages.

.An object of this;.invention= is to provide simple thermionic means'f ortimproving the frequencystability of: thermionic. generators of alternating currenta'and for controlling. wave-form and constituent harmonics of thesealternatingcurrents.

Another-object of this invention is to provide a novel phase-balancing or normalizing-device for resistance-capacitance type oscillators for balancing the quadrature-componentiof cathodeanode voltage relative to cathode-anodealternating current, together with simple thermionic means for increasing the effectiveness. of balance by restricting the wave-form of generatedia'lternating currents to substantially pure sine-Waves, to attain a highdegree of frequency stability, in the low or audio and super-audio frequency range.

,Still another object of this inventioniis to provide "simple means whereby the generators so stabilized,- can have the generated frequency also controlled or modulated byvoltagecontrol.means,

without the necessity of-a separate reactance-..

modulator tube and circuit. I

;A fourth object of-thi invention is to provide a simple device for controlling the amplitude and harmonic constituents of an alternating output voltage in relation ,to sinusoidal input-voltages including the limiting of vthe amplitude iof the output-voltage to a constant value independent of large increasesin'amplitude of'the inputvoltinvention is: f tot :provide high or. radioefrequencyl range. as welLas -th "10 lower audio-sfrequency mangemand to..provi;de voltage-control means whereby the frequency-{of --such generated .waves .can be .readily -.c.ontr.olled -or.modulated, iwithout .changeof vjvvave-sh il w.

. 7 These objectacandtothers.hereafter noted, will r135 :,be..:better mderstocd. by;reference,.to, theaccom- -panyingedrawingaand. tocthee appended claims. Referring to the drawings,

.qFig. lshows. a.funda-mentalefrequency phasebalanced thermionic alternating current, general tor, ,With1a thermionic voltagfir CQn'tr-Oh devi e: f

- -suppressing harmonicsnbyr feeding back upon a controlagrid voltages, iopposing the oscillationsustainin ,V01tageS,; after ea selected magnitude .of the oscillation-sustaining ;V0ltages has been reached; the; generator. having means for modulating .the fundamental; generated frequency, iresponsive with flha glges in bias-voltage upon the control-grid. p

Big. 2 illustrates a modification ;a6f;-Fig. 1, a

aHa t vrt re la n =imll t b i ilq e .for the oscillator, thethermionic voltage-control Ba a -e I 'th mi ni i e ra w V a voltage-control.device employing "a double-dir {40g ode, controlling the ff 'eed-back"voltagegafter a I selectable 'i'n'agnitiide .of Q feed-back voltagehas :beehreached. I g

""Fi'g .4"i1lustrates 'amdeincanen bring, 3, "containin phase-balancing impedancesgand a [parallel-irnpedance circuit'c'onnected witn't age-control device, for applying threshold mined oscillation =-opposing voltages; and permit ting different bias upon 'thelvoltage-controlde- -viceiand upona:- gridwof the thermionic genera- :35012.v r

.fiFJ ig.- 5' illustrates?azthermioniclalternating currentge'neratorzhavingj a: Hartley:-typercircuittwith f :a triode;;and :havingaivoltage control devicelavith a parallel-impedance;:circuit-,1permittingdifferent 5- bias voltages,fonsaid'deyicaandupon. the .triodef V tions' pertaining to lating purposes.

voltage relative to gcurrent. f I

grid, and having impedance means for phase-;

balancing.

Fig. .6 illustrates in graph form, a character- 3 istic of required effective-value of voltage upon' .1 a grid-oontrolelement to produce a particular effective-value of alternating current through cathode-anode, and associated network; alsoa superposed characteristic of available feed-back voltage f or producing self-sustained oscillations,

in relation to the same effectivevalues'of "cathode-anode alternating currents, and certain rela-j v conventional types of oscil- 'lators.

Fig. {illustrates in graph form, the same char-i acteristics illustrated in Fig. 6, and, in addition,

illustrates the manner in which the feed-back, characteristic can be modified bymeansof the l v devices of this invention, in reference to a threshold valueof voltage, and for determining an} 20 of voltages'in. which substantially pure sine equilibrium operating voltage within the range Waves of cathode-anode current are produced.

. vice, and by the relative phase of the superposed voltage; either degenerative or'regenerative.

Fig. 19 (I) illustrates'an impressed'sinusoidal input-voltage and a corresponding amplitudelimited, resultant voltage, obtainable from the e 7 thermionic voltage-control device, for example, as in, Fig. 17. Fig. 19 (II) illustrates certain rec- Fig. 8 illustrates a sinusoidal impressed'voltage l upon a voltage-control device of this invention,

also the effect of the constant bias-voltage of thisdevice. wFig. .9 illustrates a resultant opposing voltage, upon a generator of this invention.

Fig. 10' illustratesa tuned plate type 'alterl hating current generator, having a triode, phasebalancing impedances, and a double-diode type voltage-control device for suppressing harmonic voltage, for example with reference toFig. 8, and for use. in proportioning a threshold-determined oscillation- 1 tangular and saw-tooth Waves, and combinations, obtainable from the thermionic tube connections Fig.20, to the thermionic voltage-control device,

and to a previously described thermionic alter nating current generator.

Fig. 20 illustrates a thermionic tube with output-impedances for producing rectangular and saw-tooth voltage waves, and input-connections to grid-control meansincluding connections to one or" the types of thermionic generatorpreviously noted, 'and to the double-diode type of voltage-control device of said-generator. I

In prior art, methods have been devised for maintaining the 'feedebackvoltage of generators V employing thermionic tubes in substantial phaseopposition to cathode-anode alternatin currents, so that variations of'ztube'resistance or resistance of a phase-shifting network are to a large extent compensated; for example, Method 7 and meansfor normalizing thermionic oscilfrequencies, and stabilizing the fundamental generated frequency;

Fig. 11 illustrates a thermionic alternating current generator having phase-balancing imped-- ances, a voltage-control device, and bias-control I means for controllingormodulating the fundamental generated frequency, this generator dif- '11 fering from others'above noted, in that both the l feed-back Voltages and the threshold-determined 1' feedback-opposmg voltages are applied to ascreen-grid, leaving the control-grid free for phase-balancing voltages, and frequency modu- Fig.12 illustrates an applicationof the gen- 1 erators of this invention for purposes of frequency-mixing, and in particular the. modification of a difference-frequencyby means of a bias- Fig. 13 illustrates 'a' thermionic alternating V1 quency'phase balancing means. 7

' Fi'g. 14 illustrates a vectOr-diagramfonthe generator of Figs. 13 and 15, and shows certain important relationships employed in compensating the quadratureecomponent of cathode-anode the cathode-anode alternating Fig.sl6.illustrates a thermionic voltage-control device having a double-diodefand connections 1 to ascreen-grid, control-grid, cathode-and anode, forcontrolling alternatingcurrentsfi Fig. 17 illustrates a double-diode type t jim-c voltage produced by a conventionaldemodulator, 1 applied to one of the generators of this invention.

1 current generator particularly suitable for low 5 frequencies, that is, for audible or super-audible frequencies, and having novel fundamental-frew j i Fig. illustrates the generator of Fig. l 3, with I I a double-diode type voltage-control device, for ;,suppressingi harmonic frequencies, and for improving the frequency-stability of the generatorg lators, U.'S.-Patent No; 2,305,362, of the present inventor. frequency-stability'of thermionic generators, involve only phase-balancing for the'fundamental generated frequency, and employ a fundamentalfrequency quadraturephase voltage in. quadrature with the cathode-anode alternating vcurrents; when the voltages execute large'swings as is always-the case when the current equilibrium is brought about in the conventional manner,

7 and curvatures of the characteristics of .the'tube I are involved as well as. cut-off of anode current for a part of a cycle, then harmonic amplitudes are present to a large degree, .and phase-balancing of'the fundamental-frequency alone, cannot eliminate all undesirable phase angles. The effect of these harmonics in disturbing th balance maintained for the fundamental generated frequency, by the normalizing or phase-balancing methods'mentioned, can be visualized from the.

resultant reactance for the network connected with the cathode-anode, which can be'expressed as follows I in which'X1 is the equivalent series reactance of the network at the natural resonant frequency or fundamental generated frequency of thephase-balanced or normalized oscillator, K3 the reactance of thenetwork for the third harmonic, and in general, Xn the reactance ofthe network for the nth odd harmonic; a1s0I3/I1 iS the ratio *of third harmonic amplitude to fundamental amplitude, and in general In/Ii 'is' theratio of amplitude of nthodd harmonic to fundamental "amplitude; The reactance X1,i's normally com pensatedyin its undesired effects inf'cornbination with resistance; variations of: tube treet- -work in modifying generated frequency by'thet phase balancing or normalizing process above These processes, for: improving the,

. referred to,however,the disturbing "effect of the remainder upon theygenerated frequency is 'ap; parent, especially inview of modifications of the harmonic constituent ratios, by modification of tube parameters, cathode-anode voltagefe'tc.

An important feature of this invention, isjthe simple means for determining an equilibrium of the generated alternating current after a threshold-value of feed-back voltage 1 of "sneaable amount has been reached, and for substantially eliminating the undesired effects of harmonic amplitudes, in contributing to frequency-instabilityof the generated fundamental frequency. l V a A Methods have heretofore been employed to secure a substantial tangency or coincidence between the lower portionsof the dynamic characteristic and the feed-back voltage characteristic, by increasing the negative bias upon the grid used for feed-back voltage, thus movingone of these characteristicerelative to the other, to secure near coincidence of the lower portions. of the characteristics, through the use of rectificrs, creating a substantially steady bias of unidirectional voltage responsivefltovoltage. Such a system has certain defects which operate against frequency-stability, and which are overcome in the means for determining the equilibrium current, of this invention. Among the defects referred to, are the resort to Variation of one of the tube parameters. Thus, the grid upon which feed-back voltage isfapplied is biased more and more negatively, modifying the efiective ampli fication-factor for the grid. The dependence of effective, interelec'trode capacitance upon amplification-factor is well known, and the system above-referred to introduces undesired modifications of the tuned circuit. Further, in order for oscillations. to be positively maintained, the dynamic characteristic must operate at some curvature in such a system, to provide an equilib- :rium point, since both characteristics stem from the same origin, as will be apparent from Fig. 6, Fig. 7, discussed in further detail hereafter. In such a system instantaneous voltages are not employed for degenerative feed-back above a threshold value, only a unidirectional bias being used, and suchbias is only obtainable from rectified currents passing impedance which is substantially pure reactance at the fundamental and harmonic frequencies, since this latter is essential to providing the time-constant of the impedance suflicien-tlylarge to smooth out instanta neous current values to yield a steady unidirectional bias Voltage. lio constant externally applied bias voltage is employed to bias the rectifier anode from the rectifier cathode, nor for threshold-voltage determination, a variable unidirectional bias being created byrectification, as above noted, in such-a system.

An important feature of the present invention, isthe utilization of instantaneous voltages, of one or both polarities, the complete absence of current-created bias voltage,. and theemployment v of a constant bias, for determining a threshold-value beyond which instantaneous jdoublej'duty, for improvement of frequeney starectangular 'orsa'w-tooth ,Wave rrcm the frequency stabilized simple-harmonic waves Lso produced. An important feature of the voltage-control devicepf this finvention is the simple means employed permitting separate and distinct values offvoltag'e-bias to be utiliz'ed uponthediode or diodes, and upon the grid control-element to which thedevi'cefi's connected, a

These features; and'otherswiilbe better un- Cl erstood'from the following description, andwith reference to, the accompanying drawings.

I Referring to Fig. 1, at} 6, is 'athermionic tube, having a cathode, 4,. anode 3, control-grid I, screen-gridf2,and diode-anode 5. A tuned-grid oscillator is provided by, the tuned circuit i5 l5a-'-l5b, having the coil' l5 with resistance lea shunted by variable condenser i522, connected from screen-grid 2, to a positive potentialupon the source I I of continuous voltage-by connector He, and having a coil IE5 connected between the anode 3 and a positive potential upon source ll, greater than the positive potential upon ila the coil is having mutual inductance with l5, and the negative terminal of the source 5 i being connected to'the cathode 4. At '8, isan inductance coil, coupled with 15, one terminal of 8 being the compensating coil I'll, oneterrninalof which. is connected to the control-grid l, the"other terminal being connected .to the terminal is. Terminal .58, is connected .with terminal it, through the variable-voltage 'so'urceZl, and terminal [Bis connected with v ariableecontactor 3i upon resistance 9.1 The' variable-voltage source indicated by El is .understoodto be formodifying the resultant negative bias voltage upon the control -grid and correspondingamplification fac tor for the control-grid; tocontrol the corresponding quadrature components of cathodeanode alternating current; itfivvill be understood that such variable'voltages can be provided by a varietyof well known mea'ns for example by the output-connections of, a frequency demodulator or discriminator, or by the output-connections of electro-acoustic devices. At l2 and I3 are by-pass condensers, respectivelyfor by-p'assing the source H, or the part of source Hbetween I la and the cathodes. ,The phase of instantaneous voltages upon resistance 9, between "3| and I4, issuch as to apply degenerative voltages upon control-grid l, and also the phase of voltages set up in the compensating coil H, is in quadrature with the cathode-anode alternating currents through l6,

andithe magnitude and polarity of alternating voltage set up in l'l and impressed upon ladjustfed to, compensate the resultant quadrature component of voltage of the cathode-anode circuit at the natural resonant-frequency, and relative to the cathode-anode. alternating current.

Operation of the circuitfof Fig. 1, will be dis' Q cussedfin, further detail after other structures hereinhave been described," i v l Referring tO'FigiZ, the thermionic tubefid, has

4, ano e 3, diod node5, 'control-grjid bility by harmonic suppression ahd'for evenin "7a i -s 'l i; and" pii ss i sfld" A resonant circuit, containing the inductance coil lfia'with resistance IGb, in series with inductan ce coil I with resistance I5a, and the variable condenser I60 shunted across these coils and resistances in series, is connected to the thermionic tube to form a Hartley-type oscillator, The junc- IIb, the coil IIb being connected to .the positive terminal of source llgandthenegative terminal of source II being connected to. the cathode 4.

The terminalh, of resistance I 6b,is connected to I anode 3, and the terminal a of resistance 'I5a is connected to the screen-grid 2, through voltagereducing resistancer23 and by-pass condenser 24 l shunted across 23. ,The resistances I5a and I62) each include resistance inherent in the respective coils I5 and I6a, shunted across the choke-coil tion y of the inductance coils, is connected to the source II through the high-reactance choke-coil III) and'source II,'are'the inductance and r variable condenser 25, in series. At 9, 911, I0, Ilia,

I4,- 35, is a transfer-impedance having pure resistancesQ-and 9a, and stopping condensers 1c and Illa, the stopping, condensers being of'such capacitythat the reactance of these condensers for the fundamental generated frequency, and all I harmonic frequencies, is infinitesimal in com parison with themagnitude of resistance of 9 or'9a.

to permitthe impedance between 8d and M to be r substantially pure resistance, with negligible phase-angle, The inductance coil Bis coupled with the resonant circuit, one terminal of Bbeing 1 These condensers'serve to insulate :the separatefbias voltages employed, and otherwise} connected to diode-anode 5, and the other termi- Y nal of 8 connected to the variable contactor 8a,

upon resistance 9. At 22 is a bias-voltage source having its positive terminal connected to cathode 4. Resistance 9a is shunted'across resistance 9 through the stopping condensers IE and Inc, the;

condenser It! being connected to oneterminal of 9a and the condenser Iila'beingconnected to the other terminal of 9a. Resistance 9 is connected to a negative potential upon 22 by variable contactor I4, and resistance Sa'is connected to a negative potential upon 2'2' by variable contactor '35., Coupledwith coil- 25is compensating inductancecoil: [1. The variable contactor 3Ia upon resistance. 9a is connected toterminal I8,"W'hichi is connected'to'terminal I9, directly through conductor 20, and terminal I9 isfconnectedto'con- 5 trol-grid I, through compensating coiljI'I. For modulating the frequency of the stabilized-ire; quency oscillator, connection between terminals, I8 and I9 is through source 2| as in Fig. 1,- in- Degenerative I voltages between and 3Ia, which exist after stead of through conductor 20.

a threshold value ofalternatingvoltage determined by bias of I4 upon diode-anode 5,- has been reachedyare impressed uponr'control-grid I. Also voltages upon I! in quadrature phase with the anode-cathode alternating currents, of proper magnitude and polarity, are impressed upon con-;

trol-grid I, to adjust the oscillation-sustaining grid .2 and the positive potential upon sourceI I byi connector IIa. A greater positive potential 1 is connected upon the anode 3, through coil I6,

which coil is coupled with I5, The negative terminal of source Ii is connected to cathode 4, and by-pass condensers I2 and "I3, respectively bypass the source Ii and the part of source II from I IIa to'cathode 4; At' 22 is a bias-voltage source, with positive terminal connected to the cathode 4,1' and with a negative terminal connected by contactor 35 to control-grid I, through terminals l9ajand Isa. At 81 is an inductance coil, and at upon 8?) is a half-inductance point, the coil 8b being coupled inductively with I5; At 41 is a double-diode, having diode-cathodelar with diode-anode 5a, and diode-cathode ib, with diodeanode 5b. Cathodes 4a and 4b are each connected to a common junction through connections of negligible impedance. Connected to the junction'9c,'is the positive terminal of bias-voltage source 22a, the resistance 32 being shunted across source 22a to form a'potentiometer, Connected to the half-inductance point 8c is the variable contactor I ia upon resistance 32, one terminal of coil 8b being connected to diode-anode 5a, and the other terminal f 8b beingconnected to the diode-anode 5b. Anodes 5a, and 5b, are negatively biassed by the adjustable constant biasvcltage from 22t:-l2.- When a selectablev magnitude of. oscillation-sustaining feed-back voltage upon Z-A has'been reached, coil 86 carries alter nating currents, and the efiective resistance of the circuit I5-I5b-I5a is increased, in. relation to the threshold voltage determined by 22a 32- -1411. The characteristic of oscillation-sus-iw taining feed-back voltage in relation to cathode-'- anode alternating' currentsfis thus modified, after a selectable feed-back has been reached.

' Referring to Fig. 4, connections are similar to Fig. '3, control-grid I howevenifbeing employed both 'for impressing compensating quadrature-' phase voltages to supply fundamental frequency phase-balancing, and for impressing degenerative I voltages derived from a transfer-impedance connected between the double-diode cathodes. Thus,

connected between the diode-cathode 4a and junction 90, is the'resistance 9, and likewise conf' U nected between the diode-cathode 4b andthe junction 90, is the equalresistance 9" Shunted across the cathodes 4a and 4b, is the resistance 9a, spanning between 4a and 4b, one terminal of.

resistance 9a being connected to 4a through stopping condenser I9, and the other terminal of 9a being connected to 41) through stopping condenser Iiia, Control-grid I is connected from a negative terminal of bias 22 by contactor 35, contactor 35 being connected to a terminal of 9a, and 9a being connected by variable contactor 3 la through terminals I8 and I9, and through compensatin vcoil I1, to the control-grid I. Connection between terminals I8 and.I9,-is through connection ZlL'or alternatively, through variable-voltage source2I feed-back voltages to be in exact phase opposition".

to cathode-anode alternating currents, in order: to compensate variations ,of thermionic tube resistance, and variations of network resistance,

connected directly to cathode 4'.

7 condenserfib, andconnected between the scr'een- 75 f as previously described for Fig.1 for modulating the stabilized frequency. In thisfus'age, the resistances 9', 9", and 9a, are high in -relation to "the diode resistance, perse, between 4d and 5a;

orbetween 4b and 5b;fl:the diode curr'ents are thus very smaILtand the reaction of t'he diode circuit 'in'the resonant circuit I5'I5b-I5d is negligible, only sufficient energybeingtakenirom 'the resonant circuitto establish the degenerative a control voltages required. Referring to Fig. 5', a'Hartley-type oscillator employing a. triode, is shown, employing ;;also

phaserbalancing, and a.sing1eadiode;;witntra i9 fer-impedance connected-to diode, permitting different voltage-bias upon the diode and upon the grid. Tube to has the cathode 4, anode 3, control-grid l, and diode-anode 5. The resonant icircu it contains the coil .llia with resistance l6b, in series with the coil l5d With resistance I5e, and the variablecondenser lEc shunted across 'thege series-connected coils. The junction y of "-coils Mia and 1511, is connected through a highreactah'ce choke-coil llb tothe positive terminal 1 of source ll, the negative terminal of source ll being connected to cathode 4. The junction 72' between condenser 16c and coil lea is connected "t'o anode 3, and the junction 7" between condenser itc and coil lfid is connected through compen- 1 sating inductance coil I1 and stopping condenser 23 to control-grid l. Shunted across the source i'll: and choke-coil lib in series, is the variable (condenser in series with the coil 25. the coil '25 being inductively coupledwith coil l'l. At 22 is a bias-voltage source, with positive terminal a'negative terminal. of.22; one terminal of resistance 5a is connected through variable contac'tor to a negative terminal of 22, and the controlegrid l is connected through leak-resistance 2"! to variable contactor Illa upon resistance 9a. Degenerative voltages across s5 3la. serve to suppress the generation of disturbin harmonic amplitudes, and phase-bah 'anci'ng of the fundamental generated frequency is brought about through thevoltage introduced "into coil ii, to provide .a high degree of frequency-stability, over a range of frequencies, the condensers 28 andlsc being simultaneously tuneable, as illustrated'for example by dotted-line G indicating a mechanical connection of rotors.

Referring to Fig. 10, a tuned-plate type oscillator employing a triodeis shown, and utilizing a double-diode type voltage-control device, together with phase-balancing means. The voltage-control device is the same as in Fig. 4, the coil 81) being coupled with-the resonant circuit I60,- i6'o-l6d. The tube 6d has cathode anode 3, and control-grid l. One terminal of coil l5a is connected to the anode 3, the other terminal of coil lea being connected to choke I lb whichconnects with the positive terminal of source I l. The negative terminal of source H is connected to cathode l, and the coil 25 and variable condenser in series, are shunted across choke Hi) and source ll in series. Control-grid l is connected through coil lie, and through coil 1561, to an output-terminal 28b of the low-pass filter 28. The input-terminal 28a of filter 28 is connected by variable cont-actor am to resistance 9a of the transfer-impedance 9a-9'-9"llllla, and one terminal of resistance 9a is connected to a negative terminal of biaswoltage source 22, and to common output input terminal 230 of the filter 28. Coil li d is coupled with resonant circuit ltd-53?) led for providing self-sustaining feed-hack voltages, coil lid is coupled with 25 for providing quadrature-component phase-balancing voltages, and harmonic suppressing degenerative voltages, are provided between terminals 23c2i3a, and between 280-481). Condensers 25 and ltd can have a common rotor-shaft, for simultaneous tuning.

' Fig. 1; Fig. 2or Fig. 4. In these-figures, thecoii trol-grid 'is employed for both; phase balancing' voltages-and for threshold-controlleddegenerat tive'voltages, Whereas in Fig. 1 1; the degenerative the "coil-lha'vlith resistance it?) having one ter minal "connected to the anode 3, and the other terminal connectedto a first'teri'ninal of the highreactance' choke lib," the se'cond'terminal of the chokellb being connectedto the positive terminalof the source II, the negative terminal of sourceil' being connected to cathodes. fBia's voltage 'sour'ce 22'has its positive terminal con-'- nected to' cathode t. The screen-grids "iscon necte'd through coil it to terminal k, and't'er'minal 7c is connected through high-reactance'choke-coil l lc to a positiv potential upon' I I, through connector- I la. Coil 8' is coupld with there'sonant circuit lta wb- -liic, as is also 'coil' l 5; one ter- -mina1-0f coil-8- is connected to diode-anodes, and

the other'terminal of coilB is connected through resistance Slab-and variable conta'ctor' l4 to a negative terminal of bias-voltage's'ourc 22. 'At3,'is aground connection. 'Atlfia is"a stopping' coridenser of negligible reactanc'e, for keepingvoltage of sourcel l'fr'om the diode circuitjan'd permitting 'fiow of'alternatin'g current from terminal is to resistance Gab, through-variable 'contactorfilb upon Siab. Degenerative voltages from Qab are thus introduced upon scieen-gridZ; in series with feedback voltages from coil 1'5. Coil 25 and condenser -26, in series, are shunted across entrant and source ll in series-andcontrbl grid 'lis'con- V nected through coil '1, terminals l9 and it, to bias-voltage ofnegative polarity upon '22,'by 'va'riable contactor 35. The compensating coil l Tis .coupledvvithcoi1'25, and connections betweeh'terminals -l 3 -and -l 9 are either'direct, through connection '23 for frequency stabilization, or'thro'ugh' the variable-voltage source 2| as in Fig, 1 for I modulation of stabilizedirequency.

Referring to Fig. 12, there is illustrated in partial block-diagram form a superheterodyne reupon antenna 42, the amplifier '44 being 'commonly referred to as the intermediate-frequency amplifier, and utilized for amplifying differencefrequencies resulting from the superposition of the received frequencies at 42 and the generated frequencies of Bi, combined in the frequency: mixer 43. At'liii is a connection for coupling the network of generator '6! with the frequency mixer, in a manner Well'under'stood. Within the enclosure 4|,is shbvvn a conventional form of demodulator for frequency-demodulation and for amplitude-demodulation. Output-voltages ofin 3 -termediate-frequency from the amplifier 44 are impressed upon tube 49, for example, between 1 control-grid'SB'and ground 30.. An anode Outp'ut 3 circuit 48 'is supplied withipositive potential irom a source such as I I, Fig. 11, through conductor 5 I;

likewise a screen-grid of tube 49 is supplied with a 1 lesser positive potential from said source I I, for

example through conductor 59. At 46 is a tune able'circuit, couplediwithAB. At 41b isadouble-g' diode-tube, with cathodes 55 and 56. Connected across'the cathodes 55 and 56, are the equal resistancesZIa and M17, in series, the mid-resist ance point 2 I0 being connected through the highreactance coil 52 to the mid-inductance point upon the anode-output circuit 45, the mid-inductance point being also coupled capacitively through condenser 52a to the, anode of tube 49. In 'a ,manner' well understood, amplitudeedemodulation 'volt'ages' are provided thereby, across resistance ZIb, or 2Ia, and diiferential voltages between the extreme terminals I 8a and "Bare- ,jspectivelyof resistances 2Ib and 21a in series,

responsive to deviations of the intermediate-frequency above or below a normal value, fOrWhiChi.

the tuneable circuit 46 is exactly tuned, and for which the diiferential voltage is zero. At 45 is a connection from resistance Zlb to intermediate frequency amplifier (for volume-control, and whereby bias-voltage upon thermionic tubes of they intermediate-frequency amplifier is modified to [correct excessive volume, in a manner well understood; The'anode-outputcircuit 48 is understood 1 to be inductively coupled with tuneable circuit 46, i and each-of the two extremities of the tuneable' 1 circuit 46 to be connected to one of the diodeanodes of the double-diode 41b. 7

Such a receiving system commonly involves a considerable number of variable condensers, tuned by-mechanical connection between them, with difficulties of exact alignment, and particularly in view of modification of output-volume by the volume control. By means of a generator of this invention, terminals IB-IS can be employed to apply a self-correcting voltage, which modifies the generated frequency in proper direction, so that the intermediate-frequency or difference-frequency applied to the demodulator reduces the differential voltage across I BaI 9a to substantially zero, ,at which intermediate-frequency the tuneable'circuit, 46 is exactly tuned. By means, of the'generators of this invention, this is accomplished with a-single thermionic tube, without the necessity of" a separate reactance-modulator tube'andcircuitp 3 The generators heretofore described are best adapted to use in the high or radio-frequency range, as distinguished from an audible or superaudible range of'frequencies. The'principles of thisinvention for securing a high degree of frependent of thermionic tube variations, and com-. bining the action of phase-balancing and harmonic suppression by the voltage-control device, are also applicable in the important range of j audible and super-audible frequencies, as illus- 'trated in 'Fig;13 and Fig. 15. Fig. 13 illustrates a resistance-capacitance type oscillator'having a g novel phase-balancing means for the fundamental generated frequency, and Fig; illustrates 1 the sameoscillator of Fig 13 with both fundamental-frequency phase-balancing means and voltage-controldevice means for suppressing harmonies; to secure a maximum degree of effectiveness of thephase-balancing. Referring to Fig.

13;"at6b' is a thermionic tube havin cathod 4? anode 3, control-grid I and screen-grid 2, and having a continuous-voltage source I I with negative terminal connected to cathode 4, and a bias- 'voltage source 22 with positive terminal thereof 3 is the resistance To, and coupled with To through the stopping condensersCr and C2, is the recurrent-section resistance-capacitance network between the input terminals P-P' and output terminals Q-Q. Each section of this network consists of a resistance for the series element, designated by 21', and a capacitance designated by 22 for the shunt element, and connected to the midpoint of resistance e1, so that 'each section forms I a T, with 217 2 on either side of the shunt element ,60 quency-stability of generated frequencies, inde- 22; Connected betweenthe output terminals Q-Q' is an output-impedance consisting of a two-branch parallel circuit, one branch having the terminal resistance n, and the other branch having the condenser Cr in series with a compensating or phase-balancing resistance I'Ic. Connected from the terminal Q, isthe control-gridl,

and connectedfrom a negative terminal upon bias-voltage source 22 through variable contactor 35, is the, junction e between condenser Cr and phase-balancing resistance I10;

The resistances 21 of the sections, as well as the resistance ft and the phase-balancingresistance I'Ic, are all variable, for example bymeans of rotors such'as H, the rotors being mechanically connected together, for example by connector G, in a manner well understood. By this means, the required phase-shift for self-sustained oscillations can be produced, over a range of frequencies. The stopping condensers C1 and C2 are understood to have large capacitance, and negligible reactance in'relation to 2i and 22'.

The principles of operation of the compensating or phase-balancing resistance I'I can best be understood by reference to certain well known ,PP',- is designated by Zk, and from the wellknown principles of such structures, zk=\/z 1z2(1'+ z1/4 T a complex number, wherein Z1 is the resistance of element 21 and Z2 the reactance of element 22, that is Z2 =i/wC, where and w=21rx-frequency. This complex number can ance replacing the balance of an infinite line.

The initial current through the terminals P and P is designated by I0, and the terminal current through the terminals Q and Q by It; the relation between terminal current and initial current is then:

I It I06 NP where N is the number of T-sections referred to,

P t e: p ps eat s v f c orwf er on, a. 21 12 u er nvo v na as -s ift p r t s an to Z1 and 22, an additional phase-shift per section-of- 0 l. 5* x can be obtained, that isa total phase shift throughithe network. ofv 1r.ak, so thatthev'oltage across Q.Q' will be in exact phase-opposition with the current It. It will also be noted, that th oscillator cannot operate in an equilibrium condition with the phase-shift indicated, and fur ther, that whatever phase-shift does exist at the equilibrium condition of the oscillator, will be modified. changes in. cathode-anode conductance of the thermionic. tube, giving rise to the undesired frequency-instability." Thi will be apparent from the followingconsiderations. Iisr is the resultant cathode-anode resistance, made up of the actualthermionic cathode-anode resistance inparallel with m, and p." the resultant amplification: factor, then for the equilibrium condition of the oscillator, /E must be a vectorvoltage equal in magnitude and opposite in phase substantially limited to a singlefrequency con- 114 ofglf Pt andlor and any, change. in magni.- tude. o-t thetub e resistancechanging focal} have nce ect upon the magnitudeof generated fredueey,- so long. as. a single, simple-harmonic generated frequency is concerned,

It is therefcfre evident, with thecompensation crphase-balancing of this oscillator, as with the other oscillators herein disclosed, that a maximum effectiveness of the-phase-balancing can only be utilizedwhen the generated frequency is stit ientv in the. generated alternating currents.

illustrates how this is accomplished for thepscillator of Fig. 13, employing .thevoltage control device of this invention. The phaseshifting network is identical with Fig. 13,,also

- the connections to the thermionic tube, however,

to the vectorsum of voltages E5- and IoTp, where ET is the terminal voltage across Q-Q, E0 the voltage. across P-FP, and 1073; the cathode-anode voltage drop. This vector will be along a lin somewhere intermediate between Euand Iorp, and Eewill have to have anupward component, to compensate the downward component IoXk of E0. Also, when this particular equilibrium is determined, and the oscillator runs at the requifrequency. tor this equilibrium, it is apparent that any change in cathode-anode tube resistance will upset this balance, and generate a new frequency.

T avoid this condition the compensating re sistance lie is provided By thi means a quadrature-component of voltage isprovided upon the control-grid it, in quadrature with ET, and in such magnitude and polarity as to compensate for the quadrature component of voltageof E0, that is the reactive-component of voltage occasioned by the cathode anode alternating cur rent flowing through the characteristic impedance, and indicated by I Xk. The resistance employed at l'lc is small in relation to thereactance of condenser Ct, so that the current, through {To is determined in. magnitude and phase by the reactance of C and the terminal voltage ET. It will be noted that the summation of voltages upon the control-grid takes place in-the sequence HCQ'Tt-Q-l, and that resistance He can be adjusted relation to the resultant amt plification factor ,LL', to Ct, and to the parameters Z1 and Z2 determining characteristic impedance, phase shift, and attenuation, so that IoXk will be separately compensated, for all operating frequencies; under these conditions the voltage ET when amplified, need only sustain the arithmetic tl e' connections fromQbia's-source 22 to controlgrid 1, include connections with the resistance to; of the transfer-impedance. Coupledwith the resistance 1.0, are the equal resistances, 8d and tie connected in series, and having the common junction 87', a terminal of 8d being connected to one terminal of To through condenser C3, and a terminal of 8c bein connected to the other terminal r0 throughcondenser C4. The doubledicde 4'! has diode=-anode 51) connected to a terminal of 3d opposite. common junctiontv} and diode-ancde 5a connected to a terminalof 8e opposite common junction; 87". Cathodes 4 and 422 areinterconnected by the transfer-impedance 5,' i-lj'-' lfifirfill-r-lfi; previously. described, a positive te minal of bias voltage source z being connected, to junction Sc between 9and 9", and

negative terminahof 22:! being connected I through variable contacto- Ida to the junction The terminal e of the compensating resistancei tic, is connectedthrough variable contactor 35a; to'resistance 8a, and a terminal of is connected to a negative terminal of biasvoltage source 22 through variable contactor 35, to apply threshold-determined degenerative volt ages upon control-grid l, in addition to quadrature-component compensating voltage from l-lc, and oscillation-sustaining feed-back voltages from Q-.-Q'. The thermionic tube illustrated for Fig 15, at to, has a suppressor element 1 con-- nected to cathode 4; connections of other elements are identical with Fig. .13. Condensers Cs and C4, are large capacity stopping-condensers, and have negligible reactance in relation to the resistanceslid and. 86;

Referring to Fig. 16 and Fig. 17, at 15 and i5 input-terminals for applying alternating voltage to the input-impedance i5g l5k. Coupled with the inductance coil |5lc is the coil 8b, one terminal of 8}) being connected: to terminal ill, the other terminal of 322 being connected to terminal F2 and the mid-inductance point of 8b being connected to terminal ll. A doublediode it, with transier impedance, and bias voltage connection, as previously described, is connected to terminals t8, i -l and I2, terminal "5'5 being connected to diode-anode 5a, terminal "53 to. diode-anode 5b, terminal ll to a negative terminal oi bias-voltage source 2204, and the positive terminal of 22a connected to the junction 96 between 9 and 8", upon the transfer-impedance iiK-Q' 'l llw8q-i l} interconnecting the cathodes la and 4b. Terminal It is connected directly to. the cathode do, and terminal vl4. connected directly to cathode 4b, resistances 9' and 9 of the transfer-impedance being connected in series. between T3. and M. The dottedline control-device enclosure designated by. 90.,

. type 15 Ill, II, the above-described connections thereto of double-diode 41, bias-Voltage source 22a, and resistances 9' and 9"; for simplicity of illustration these connections are referred to in Fig. 17 andFig..20 as the control-device9U. Referring in particular to Fig. 17, and to Fig ltl, the various relationships-of. resultant voltage at the terminals 85'-85 obtainable from impressed voltages upon I 'i6,.will be apparent. The relative phase of the threshold-determined voltages 12 13' and, and

upon' 9a combined with the voltages from IE-1,5, is"contr'ollab1e by the variable-contactors em and 35upon 9a; the characteristicindicatedat A, Fig. 18, shows the resultantsvoltage across 85 66 when they contactors em and 35 are coincidentupon'the same point upon 9a,'andno voltage is combined 'from'9a. When voltages are introduced at 9a, by separation of'3I a and '35 so as to have phase-aidin or regenerative components, the resultant characteristic is rowith reference to the coupling of coil8b with. resonant circuit I5-I5a'-I5b, and the connections 35 and :3Ia. At-Sb' is a thermionic tube V tated in a direction indicatedby arrow 33, for

example along a characteristicsuch as B, and with reference to the threshold voltage at q;

when the separation at 3Ia and isof opposite order in reference to path traversed through 9a, then the voltages introduced from 9a are phaseopposing or degenerative, and the resultant characteristic is rotated in a direction indicated by arrow 84, for example along charaeteristics such as C, D, or'F, with reference to threshold voltage at q'." A high degree of waveform control is thus provided, and in particular when large magnitudesof opposing voltage are employed in relation to the magnitude of impressed voltage. For example, with the characteristic D, after the threshold value of voltage (1 is reached, increments of impressed voltage are opposed by equal increments of voltage from 9a, and the resultant voltage at 8685' is coni6 Referring to Fig. 20, a device is illustrated for generating irregular-shape waves, such as rectangular and saw-tooth waves, from a generator .for a second thermionic tube supplied with stabilized-frequency voltage from the oscillator. At 90 is shown part ofthe double-diode voltagecontrol device, previously described, and for example as connected ,to the oscillator of Fig. 4,

with cathode 4, anode 3', control-grid I, screens grid 72' and output-impedance Z in series-with Z", connected between anode' 3' and the positive terminal of continuous voltage source I I. AcondenserS'I is shunted across the terniihals'H-BB' of Z',' the condenser bein variable, and I8 isa terminal of Z" connected to the positive terminal of source II.

Screen-grid 2 is connected, for example, directly to terminalillt, Fig. 4, that is to'screen-grid 2, Fig. 4. Stabilized-frequency isimpressed upon screen-grid 2', and by means of the variable contactor 3Id upon 9a connection is made to control-grid l',for wave-form control. 'For example, when the variable-contactor 35d is adjusted for applying opposing voltages to I' in excess of a threshold magnitude, rectangular current waves are produced through the cathode-anode circuit 4'3'; if Z is a variable resistance, and

voltage wave is produced across the terminals 18-88 of Z", and anisoceles-triangle' type sawstant as to maximum value, independent of greater voltages impressed at 'I5'I6. By this means, trapezoidal-type waves can be generated, as indicated at 8!, Fig. 19, and also rectangularwaves, a by employing sufiiciently small threshold-voltage in relation to maximum voltage of the impressed signals at 15I6.

tooth wave is produced, across the terminals TI88. Thesewaves are illustrated respectively in Fig. 19, part (II), at BI and88. The total I voltage across II-88 is a saw-tooth wave indicated by 81', and the successive right-triangle type saw-tooth wave can be produced from 81', as shown at 81", by invertin alternate waves through rectifier means, in a manner well under- Modification of harmonic constituents, is considered in further detail hereinafter, and with reference to certain quantitative relations. The device illustrated'at 953, Fig. 17 and Fig. 20, is under stood to contain a double-diode 41, bias-voltage source 22a, and connections between terminals 'Iil,-lI, 72, I3 and 14, identical with those described for Fig. 16.

-In Fig, 1'7, a thermionic tube 611, having oath} ode 4, anode 3, control-grid I, and output-impedance Z connected between anode 3 and positive terminal of source I I is shown, the'resultant voltage between terminals 86' and 35' being directly applied to the control-grid I, from a negative terminal of the bias-voltage source 22, for controlling thermionic current through Z, i

In Fig. 16, thermionictube 61) has cathode t, anode 3, control-grid I, screen-grid 2, and output-impedance Z connected between anode 3 and a positive terminal of continuous voltage source grid I, from a negative terminal of bias-voltage source 22.v

stood. It will be understood, that portions of such saw-tooth waves are in fact portions of exponential transient changes, and that such portions can be made to approach straight-line changes with time, by employing a sufiiciently small portion of such transient characteristics.

Having described the principal structures of this invention,'certain important features of operation of the devices will be apparent from the following considerations. Referring to Fig. 6 and Fig. '7, graphs are shown, illustrating equilibrium currents in the cathode-anode circuit of conventional oscillators, and Fig. 7 illustrating control of the equilibrium current by the devices of this invention. Relative to origin 0, ordinates indicate the efiective Value of cathode-anode alternating current, designated by ip, and abscissas indicate efiective value of a grid voltage, 6g, either required to produce i or available upon the phase-shifting network when the current ipis produced by separate excitation of the grid. For

example, 36 illustrates a relationship between current 211 and grid voltage at for a separately excited thermionic. tube with a phase-shifting network connected between cathode and anode, and 31 illustrates corresponding voltages available across the part of such network which would normally-be connected to the grid when employed as an oscillator, and for any particular current 17 i At bis an equilibrium point, at which the voltage required to produce the current i is exactly equal to the voltage available for feedback, at 2'1). For currents less than that indicated at p, the available voltagefor feed-back is greater than required, and for currents greater than indicated at p, the available voltage for feed-back is less than reguired. Equilibrium at-- tained in this manner in conventional types of oscillators, commonly involves large voltage swings, and operation employing the dottedportions of the characteristic, upon which cathodeanode current is modified'oy cut-off, for portions of a cyclerand substantial curvatures are traversedupon th tube characteristics; the resultant alternating currents thus contai nurnerous har monic frequencies. Referring to Fig. 6, there is illustrated the eifectof certain methods hitherto employed for constraining the equilibrium operating point to a' more favorable position upon thercharacteristics, for example at p, by moving thecharacteristics relatively away from each other, as indicated by the arrows 36a and 37a.

For example, diodes have been used to establish a current-created steady-voltage negative bias upon a grid, increasing with increase in voltage swings, and thus reducing the amplification factor of the tube, and decreasing the initial slope of curve 36. Certain important disadvantages of this method for use with frequency-stabilization devices, have been previously noted herein. It will also be noted that for positive operation, in building up to the equilibrium current, the available feed-back voltagemust be definitely greater than the voltage required for any current ip, below the equilibriumcurrent; for example as indicated by the marginal amount uv, at the particular current indicated by the line 1). Thus, som residual curvature must be retained by this method, which is limited ,by the fact that both characteristics in the range desired, are substantially straight lines from the same origin, 0. i

Fig. 7 illustrates the principles of this invention, applied to a thermionic oscillator, and shows the utilization of a virtual-origin for instantaneous threshold-determined degenerative voltages, for controlling th feed-back characteristic, without the necessity of modifying the dynamic characteristic, and without introducingthe disadvantages attendant upon modification of tube parameters. At q, is shown a virtual origin, determined by the selective voltage of the constant bias, negatively biassing the anode or anodes, of the diode of the voltage-control device. At 38 is indicated the degenerative voltage c for any current i 'the'resultant feed-back characteristic being shown by Ocp. It will thus be seen thatby selective control of the constant negative bias voltage upon the diodes 4-5, or 41, and by selective control of the amount of degenerative feed-back voltage, the equilibrium point p of the oscillator .can be readily controlled, and the oscillator constrained to operate in the range of grid voltages desired. By this means an ordinary feed-back characteristic, such as O-qp, is modified to.O-.-qp40.

1'8 65 resulting from a single diode, and waves 65 and 66 resulting from double-diode rectification. At c is shown an instantaneous value of such' rectified voltage.

In orderto aid in visualizing modifications in,

ing quantitative relations are noted, it being understood that these relations rare notto be construedas any manner of limitation upon the employment of the 'structuresjhe rein described, or otherwise than to facilitate a betterunderstanding of the principles employed to stabilize the generated frequency, in

previously described j n Designating the fractional part of the maximum voltage Ea which is employed for constant negative bias-voltage upon the diode or diodes of the voltage-controldevice by 1 /Y, then 7 Eb=Ea/Y The rectangular bias-voltage 163, Fig. 8, opposing the voltage 54, expressed in terms of the wellknown Fouriers series expansion is:

in whicht is elapsedtime, and on=2wic1?)i, n being the order of odd harmonic, and Fn the frequency corresponding to the with odd harmonic. The

impressed voltage-upon the diodes is: .l i w -el1=Ea sinwrt l The resultant voltage,' 65, 65 is-thus:

andwhena fraction defined by 1/1 o th rcsultant voltage is degeneratively.ccmb nedrwit a vo1taee...such as 64.:the resultant voltage is:

Referring to Fig. 8, and Fig. 9, at '64 is shown a sinusoidal voltage .wave, the horizontal axis being proportional to elapsed time; at .eaisjshown an instantaneous value of voltage, at, Ea the V Sill wgi-I- 1; Sin w t An estimate offthe harmonic constituents, with particular reference to the {large "reduction in harmonic content of the fced bacK voltage, when the ratios l/Y 'andl/pare small fractions, for

frequency stabilization "purposes, i readily obtained'bycOMPhtifion .oi the amplitude of 'nth harmoniclpresent with the amplitude of the fundamental. Thus the ratio of amplitude of w th "odd harmonic t fundamental amplitude is:

l v i1 n 5 l4 2 m As employed in its fullestscopa asdesc-zibed with reference to Fig. 18, for generation and control of wave-form of irregular waves, the degenerative voltage of the voltage-control device.'can be equal to, or greater than, corresponding incre- ,ments .of impressed voltages, beyond. thethreshold value, as in characteristics D or F, respectively; Fig. 19, part (I) for example, illustratesat 82 degenerative voltages equal to the excess-10f impressed voltages .80, above a negative biasvoltage suchas 8!; :Itwill be evident that con.-

scillators such as.

. 1 sin n embodiments, or otherwise than by the terms pling between the diode 4'! and source of im'- pressed alternating voltages, for example between coil8b and |57c-l5g, Fig. 16 or Fig. 17, can be such as to impress upon 8b greater voltages than are present upon l5k-l5g. V 1 1 V For simplicity of illustration, bias-voltages havein each instance been shown with reference to a batterysource. It will be evident that other well-known source-means for negative bias can beemployed, for example utilization of voltagedrop caused by flow of steady-component of cathode-anode current through a resistance, 0on nected to a cathode,for example to cathode 4.

' Having described several illustrative embodi ments of my invention, it 'will be evident that changes can bemade in the form and arrangement of parts, and by substitution in part of other well-known structures, without departing fromthe spiritjof my invention, as set forth in Q; the appended claims, and' I do not therefore providing oscillation-sustaining feed-back volt ages, and a fundamental-frequency quadrature phase feed-back voltage means for regulating.

phaseof resultant voltage impressed upon said I anode-cathode circuit, of a frequency limiting device, for limiting the wave form of the generated alternating currents to a sine-wave of said fundamental frequency, said device having a closed conductive circuit comprising the series connection of a constant-voltage bias means, a

thermionic-diode means having a diode-cathode and a diode-anoda'a coupling means coupledwith saidphase-shifting network, and'an imped ance means capable of carrying the total current passing through said diode means, comprising,

substantially pure resistance to said fundamental frequency and. to harmonics of said fundamental 7 frequency, for providing thereon synchronous voltages of substantially equal phase to the oathlimit the'scope of the invention to such particular the appended claims. 1

What is claimed is:

1. In a thermionic alternating current generator having a thermionic tube, and a phaseshifting network with an alternating current input-circuit connected between a cathode of said i tube and an anode of said tube, and with an output-circuit connected to said'cathode through a connection of substantially zero impedance,

ode-anode alternating currents of said generator;

and a conductive connection from agridof said thermionic tube to said cathode of saidtherm providingoscillation-sustaining alternating feed;

back voltages, a harmonic suppressor device for limitingthe wave form of the generated alternating currents to contain substantially only amplitude variationspf a; single frequency, said dc;- V vice comprising a constant-voltage bias means, a thermionic diode means having a diode-anode ionic tube includin -a degenerative coupling with b said impedance means; a first terminal of said coupling means being connected to said diode-q anode, a second terminal ofsaid cou'pling' means 7 being connected to a'negative terminal of said bias means, and the positive terminal of said bias means being connected to saiddiode-cathode, for negatively biasing said diode-anode from said diode-cathode. V

4. The combination with a thermionicalter-i nating current generator, having athermionic tube, a phase-shifting network with-an mama: ing; current input-circuit connected between a cathode of said tubefand an anode of said tube,

V and with an outputecircuit connectedfto said and a diode-cathode; and a'coupling means coupled with said phase-shifting network, said means being seriallyconnected and forming a Iclosed conductive circuit; a first terminal of said coupling ;means being connefizted to' said diodeanode, asecond'te'rminal of said coupling means being connected to a-negative terminal of said bias means, and the positive terminal of said bias means being connected to gsaid diode-cathode, said voltage bias means negatively biasing said I diode-anode from diode-cathqde;

In combination with the structure of 01am! 1,;impedance means connected in' series with said serially connected means, carrying the total cur,-'

rent passing through said diode means, comprisiing substantially pure resistance to said. single; frequency, and to harmonic frequencies of said single frequency, for providing voltages thereon synchronous with, and without substantial phase cathode through a connection of {substantially zero impedance, and a fundamental-frequency quadrature-voltage feed-back means for compensating undesired phase-shift of resultant voltage in said anode-cathode circuit, produced by-variations of thermionic resistance between said cathode and said anode,and by variations of resist-. ance'of said network, of a frequency-limiting device for limiting wave-form of the generated alternating currents to a sine-wave of said fundamental frequency, said device having a" closed' conductive circuit comprising theseries' connection of a constant-voltage bias means, a1 therrn= ionic diode-means having a diode-cathode and'a displacement' from the alternating voltages in said coupling means, and a connection from a grid-elementof said thermionic tube to said cathjode 'ofsaid thermionic tube, including a degenerative-coupling with said impedance means, for

' impressing upon said grid-element said synchronous voltages in substantial phase opposition to 7 said oscillation-sustainingalternating feed-back voltages,, only when a selectable limit of alternating current in said input-circuit hasbeen 7 reached. 1

- 3. The -combination with a thermionic falter hating current'generator', having athermionic tube, a phase-shifting network with an alternatif current input-circuit 'connectedbetween a "cathode jand' ananode of said tube, and with an "outputcirc'uit connected to said cathode'through j a connection of 1 substantially zero" impedance diode-anode, a coupling means coupled with said phase shifting network, and animpedance means carrying the total current through said diode means, comprising substantially pure resistance for saidfundamental frequency, and for har 3' monics of said frequency; a conductiveconnection from agrid of said thermionic tube tosaid cathode of said thermionic tube including a defgenerative coupling with said impedance means,

a first terminal of said coupling means being connected to said diode-anodaa second terminal of said vcoupling means being;connected to a, negative terminal of said bias'means, and the positive a terminal of said bias means being connectedlto' said diode-cathode, for positively biasing said diode-cathode from said diode anodeg A} l 5. 'Thefrequencycontrol system, havin athen mionic oscillator comprisin a thermionic tube I with 'a cathodejan anode, a first'control gri'd adjacent said cathode, and a secondfcontrol-grid between'said first control-gridand said an 'e sired capacitive currents normally-inherent}with V 'changesof voltage between saidfirst control -grid 2.1 and said anode, a tuned phase-shifting network for determining the fundamental frequencylof said oscillator, having an alternating voltageinput-circuit connected between said cathode and anode, andan alternating voltage output-circuit said first control-grid and said: cathode serially including connections with said impedance means V and with a bias-voltage controlmeans for controlling negative bias of said first control-grid, and a source of unidirectional supply voltage with a positive terminal connected to said second con trol-grid and to said anode, whereby undesired extraneous detuning of said phase-shifting networkthrough bias-voltage variation of said capacitive currents is eliminated, and whereby desired-control of said frequency is effected entirely by said quadrature-phase voltages without preamplification of said quadrature-phase voltages.

6. In combination with the structure of claim 5, a harmonic-amplitude eliminating device for substantially eliminating amplitudes of harmonic frequencies of said fundamental frequency, said device having a closed conductive circuit comprising'the series connection of a constant-voltage bias means, a thermionic diode means including said cathode witha diode-anode, a 1 coupling means coupled with said-phase-shifting network for providing voltages of like phase with currents through said anode, and asecond impedance means carrying the total current from said diode means, comprising substantially pure resistance for saidlfundamental and harmonic frequencies; v said circuit between said first control-grid and said cathode including a coupling-with said second impedance means transferring to said first control-grid oscillation opposing voltages, and said closed conductive circuit having a first terminal of said coupling-means connected to said diode-anode, a second terminal of said coupling means connected to a negative terminal of said constant-voltage bias -means, and the positive terminal of said constant-voltage bias means connected to said cathode, positively biasing said diode-cathodefrom said'diode-anode and providing a threshold-control of said transferred voltages.

, I '7.-A voltage limitingidevice for limiting alternating voltages to a selectable magnitude, saiddevice comprising a first impedance for applying said alternating voltages, a thermionic regulator ond impedance, and'a second coupling means between said first and second impedances for jointly applying alternating voltage from said first impedance and bias-limited alternating voltage from said second impedance.

8. In combination with the structure ofvclaim 7, a thermionic tube having a cathode, an anode, and grid meansfor controllingthermionic. currentssbetween .said cathode and said anode: a third impedance connected between said anode and said cathode, a continuous voltage source connected with saidanode, .and the connections between said grid means and said cathodeincludin'g a connectioniwithlsaid first impedance and a connection with said second impedance, controlling said thermionic currents difierentially,

-by-alternating voltagefrom said first impedance and by said bias-limited alternating voltag from said second impedance, for limiting thermionic alternating currents through said third"imped ance. l

9. A resistance-capacitance thermionic alternating current generator having a thermionic tube with a cathode, an anode, and grid-control means for controlling thermionic currents between said cathode and said anode, an input-resistance connected between-said cathode and anode, a continuous voltage source connected to said anode, a recurrent-section resistance-capacitance phase-shifting network connected to said inputresistance, having :a characteristic input-impedance, and having the capability of producing a total phase-shift ofv output alternating voltage relative to input alternating current of degrees,'an output-impedance connected to the'output-end of said phase-shifting network, equal at each frequency to said characteristic impedance at said frequency, a thermionic current-limiting means limiting alternating Icurrents in said cathode-anode circuit, a compensating-impedance coupled with said output-impedance, for providing a componentof alternating voltage in quadran tore-phase with the alternating output-voltage across said output-impedance, to compensate the quadrature-phase component of alternating voltage in' said cathode-anode circuit established by cathode-anode alternating currents through said characteristic: impedance, and connections from said grid-control means to said cathode including connections withsaid output-impedance and with i said compensating-impedance.

10. In combination with the structure of claim 9, means for selectively controlling the generated 0 frequency of said generator, including th simul 5 V taneous modification of resistances of said recurrent-sections, said output-impedance, and said compensating-impedance, and the mechanical connection of rotor-members controlling said resistancespw nereby a selectiv frequency generator is provided; having a high degree of frequency stability substantially independent of variations of thermionic resistanceof said tube, and free from substantial harmonic amplitudes of said selected frequency. r

11. Anelectrom'c wave-form'control device, for controlling-wave-form of alternating voltages, said device comprising an input-impedanc for applying alternating voltages, a coupling-impedance coupled with said input-impedance, having a first terminal, a second terminal, and a halfimpedance terminal, a constant-voltage bias means, a thermionic double-diode having a first diode-cathode and a first diode-anode, and a second diode-cathode and second diode-anode, a

transfer-im edance connected between said diode-cathodes, comprising a first resistance connected between said diode-cathodes, with a second resistance having one terminal thereof connected to said first diode-cathode through a first condenser, and having the other terminal there- V of icon'nected to said; second;diode-cathodeI through a'second condenser,said first and second condensers havingiinfinitesimal impedance in 1 relation to said first and-second resistances; said 5' 5, a diode-modulator device-for modulatingthe first terminal of said coupling-impedance being 3 connected to said first diode-anode, said-second terminal'of saidcoupling-impedance beingcon-w nected to-said second dide-anode,,a connection from a negative terminal upon said constantvoltage bias means to said half-impedanceterminal, a connection'from thetpositive terminal of saidiconstanto-voltage bias. means to the half-resistance point upon said first resistance, and cir,-, cuit connections, including-a connection between saidsecond resistance. and said input-impedance,

jointly applying voltages from said second resistance and from said input-impedance.

12. In combination with the structure of claim;

11, a thermionic f alternating, current generator having a thermionic tube with a grid-control element, and having a phase-shifting network ,.in-

cluding said input-impedance, said'circuit connections including a connection with said gridcontrol element. 1

13. In combination with the structure of claim 11, a thermionic alternating current generator having a first thermionic tube withgrid-control means, and with a phase-shifting network," and a second thermionic tube with, grid-control means, said phase-shifting network including said'inputimpedance, said circuit connections including con ,nections with the grid-control means of said first thermionic tube and. connections with the gridcontrol means of said second thermionic tube, in-, cluding connections with said phase-shifting network and with said second resistance, whereby stabilized-frequency voltages are produced, and thewave-form of said'voltages controlled.

14. A control-device for controlling the magni- 1 tudeand form of electrical impulses, said device having an input-impedance for applying said impulses, a thermionic regulator means, and animpulse combining means, said regulator meansineluding a transfer-impedance having a first 'ter minal, a second terminaLja resistance interconnecting said terminals, and a third terminal at the half-resistance point upon'said resistance,.'a voltage bias means having one terminal connected to said third terminal, a first conductive circuit from the other terminal of said bias means to said first terminal including a first dioderectify+ ing means having a first diode-anode, a-second conductivecircuit from said other terminal of said bias means .to said second terminalrincludinga second diode rectifying means havin a second di ode-anodef'said first conductive circuit'including a V first coupling-impedance coupled withsaidinputimpedance, saidsecond conductive-circuit including a second coupling-impedancecoupled with said input-impedance, and said bias means applying negative potential-to said diode-anodes for biasing said rectifying means,;andsaid impulse 24 combining means including a commonconductive connection gebetween' said input impedance and said-transfer-impedance. V. i t

, 15. In combination with theistructurefof claim amplitudes of the cathode-anode alternating, currents, said device havinga closed conductivecir-r cuit'serially including a second bias-voltage control means,..a transfereimpedance, a thermionic l0 diode with a diode-cathode and a diode-anode;

and a coupling means coupling said closed circuit with said phase-shifting network, saidsecond bias control means controlling the amount of negative bias of said diode-anode fro saiddiode-cathode,

l5 and saidconductive connection including a' eircuit through said transfer-impedance, for threshold control of feedback-voltages of opposite phase tosaid cathode-anode alternating currents.

16; The :combination with a thermionic ,ampli- 20 fier of a current-limiting device for limitingithe a constant bias-voltage. source, a transfer-impedance, and a coupling meanscoupledwith said out- 7 put-impedance, said bias-voltage negatively bias 7 ing said diode-anode'fromtsaid cathode, and a second coupling means coupled with said transfer-impedance, connected in series with said input-impedance between said grid and said cathjode, for transferring said transfer-impedance, to .saidgrid. v

40 17. A control-device for controlling the magnitude and shape, of cathode-anode current impulses, in a thermionic tube having a cathode, an

anode, and a grid for controlling thermionic currents between saidanode and said cathode, said control-device having a conductive input-impedance for applying Voltageimpulses, a-thermionic' voltage-regulator comprising a closed conductive series circuit every part of which is, conductive, said; circuit having the series, connection ofacon- 'stant bias-voltage mean :athermionic diode,

means with a diode-anodeand'jdiode-cathode, a

transferdmpedance, and acoupling' means for coupling said diode means with saidinput-imped-J:

ance,said bias-voltage means beingconnected to 5 5 negatively biassaid diode-anode from said diodetransfer-impedance in series, for jointlyapplying to said grid the impulse-voltagesupon saidiinput impedance and upo'nsaid transfer-impedance;

P T I EDWARD H. LANGE. V

alternating voltages from cathode; and conductivecircuit connections from said grid to said cathode including a conductive circuit through/said inputeimp'edanceiand" said 

